Safety restraint technology relies on woven fabrics as the principle material of construction. On impact, gases are generated instantaneously to inflate the bag. As the pressure within the bag increases during deployment and later from passenger contact, the airbag fabric stretches in a biaxial-manner. Passenger contact with the slowly deflating airbag accelerates the gaseous outflow through the fabric, airbag seams, and through specially constructed vents. A fraction of the impact energy can also be adsorbed by mechanical biaxial stretching of the fabric's fibers. However, the fabric's permeability and/ or vent system appear to be of primary importance to energy dissipation.
A unique blister-inflation technique was developed and used to evaluate the fabric properties necessary for energy dissipation by these four mechanisms. The performance of fabrics woven from two traditional commercial polymeric fibers offered for airbag construction were considered. These materials are: the traditional polyamide nylon 66 and a high strength poly(ethylene terephthalate). These two fabrics, with differences in fiber denier and weave, were evaluated for five different inflation temperature levels and at eleven different pressure drops.
A kinetic-energy model was developed to account for the energy that should be dissipated by the above mentioned mechanisms. The importance of vents with respect to the energy dissipation point of view was reported by earlier investigators. This paper, however, focuses on and compares airbags made from the above mentioned polymeric fibers which contain no vents. Based on the proposed model predictions the existing airbags appear to be adequate with respect to their ability to dissipate energy over a rather short time frame.